1887.] NATURAL SCIENCES OF PHILADELPHIA. V.)\} 



ical cells of nearly uniform size, made polygonal by contact, charged 

 with multitudes of spinous acerates. 



Skeleton spicules slightly curved, smooth, rather abruptly pointed. 

 (PI. VIII, fig. i, ii, iii, iv. a, a, a.) 



True dermal spicules wanting. 



Gemmule spicules or those embedded in the parenchyma, (1*L 

 VIII, as above, b, c. etc.) either cylindrical or larger at the middle 

 and slightly tapering toward the extremities, which are truncate, 

 rounded or with a single terminal spine; entirely spined ; spines 

 erect, conical or rounded; generally largest near the ends of tlie 

 spicule. 



Approximate measurements. Diameter of gemmules 0.02 inches. 

 Length of skeleton spicules 0.0075 inches ; of gemmule spicules 

 0.003 inches. 



Sab. Standing or running water everywhere ; rather affecting 

 the former. 



Loc. In all parts of North America heard from ; Europe etc. 



The proper identification of this sponge which was the first de- 

 scribed as discovered upon the American Continent, has become a 

 subject of particular interest on account of its recent discovery :it 

 several points in the Eastern Hemisphere. The original description 

 by Prof Leidy has just been quoted. It will be remarked that al- 

 though the date of its publication was a dozen years prior to that of 

 Dr. Bowerbank's "Monograph" (1863) the name does not appear in 

 his list of species. This is explained by the absence of illustrations 

 from Dr. Leidy's text and the unfortunate circumstance (as narra- 

 ted by Dr. B. in his description of Meyenia leidyi,) that the sponge 

 sent to him marked ''S. fragilis" did not correspond with the accom- 

 panying description, but proved upon examination to belong to a 

 novel and quite different species. 



Dr. Bowerbank consequently ignored S. fragilis as imperfectly 

 described and was followed by H. J. Carter in a similar omission. 

 I take pleasure in restoring the name to its proper place in the lit- 

 erature of the subject, associating it with the species now described 

 for the following reasons: 



In 1878 or 1879 my attention was first attracted to the subject of 

 fresh-water sponges by the discovery of a few gemmules, resembling 

 a rust-colored incrustation, upon a stone from Lansdowne Run, 

 Philadelphia. Noticing the variation of the truncate flesh spicules 

 from the pointed acerates in the descriptions of *S^. lacustris and S. 



